Circuit for amplitude modulation carrier wave



MODULATION POTENTIAL 500/205 I I I R. URTEL Filed Oct. 27, 1936 POTENTIAL SOURCE CARR/ER WA VE SOURCE CIRCUIT FOR AMPLITUDE MODULATION CARRIER WAVE Al lg. 29, 1939.

MODULATION POTENTIAL SOURCE INVENTOR RUO URTEL BY AWQRNEY Patented Aug. 29, 1939 UNITED STATES PATENT OFFICE CIRCUIT FOR AMPLITUDE MODULATION CARRIER WAVE many Application October 27, 1936, Serial No. 107,816

Germany. November 22, 1935 5 Claims. (Cl. 2509) The invention pertains to systems as disclosed in my United States application #595,519 filed August 12, 1936.

In accordance with the invention the modulation of the carrier wave with several potentials is to be accomplished in the manner that these potentials are fed to separate electrodes of discharge tubes disposed in one or both branches. In what follows two embodiments of the invention will be described as illustrated in Figures 1 and 2 of the drawing. In Figure 1 modulating potentials from two sources are impressed on wave 25 energy by means of a single tube of the multielectrode type. In Figure 2 two tubes are arranged to modulate a wave by two controlling potentials.

l in Figure 1 represents a hexode and T1 and T2 two transformers, the first being provided with one primary and two secondaries, the second with two primaries and one secondary. Primary ll of transformer T1 is fed by energy from a carrier frequency generator and the secondary 12 of this transformer is connected in series with a modulation potential source M1 in the circuit between the cathode 8 and grid I of the hexode 10. The secondary 13 of the same transformer feeds the primary I4 of transformer T2 whose primary is connected in the plate circuit of hexode Ill. The circuit of grid 3 of hexode contains a second modulation potential source M2 while grids 2 and 4 are connected to a suitable positive potential source Hi.

The arrangement according to Figure 1 operates in the manner that the plate alternating current of tube l0 having carrier frequency is modulated with the frequencies of potential source M1 and M2 and that the fieldsof windings l4 and I5 have opposite action with respect to each other. Thus in the absence of modulating potentials the carrier portions in i5 and I oppose but are related and adjusted to produce a finite carrier with no modulation. In the presence of modulation potentials from say source M1 the above condition no longer holds and modulated carrier energy modulated in accordance with potentials from M1 goes out. Now if modulating potentials from M2 are impressed on grid 3 the carrier in I! is also modulated in accordance with said potentials. A potential of carrier frequency may therefore be taken from secondary ll, modulated to a higher degree from the plate alternating current of tube 10.

In contrast to the arrangement illustrated in Figure 1, the scheme shown in Figure 2 provides controllable discharge tubes, again hexodes l8 and 19, in both branches connected in parallel. The carrier frequency potential is fed in phase opposition to grids 3 through a transformer 20 whose secondary midpoint is grounded by way of a negative biasing potential source 2|. The two modulation potential sources M1 and M2 are disposed in the circuits of grids l of both tubes and are connected in series with a negative biasing potential sources 22 and 23. Grids 2 and 4 of both tubes are impressed with a suitable positive potential by potential source 2Q. In the joint plate current branch is connected a current resonance circuit 25, tuned to carrier frequency, and a plate potential source 26.

This arrangement operates in the manner thata plate alternating current appears in each of the two tubes modulated with the frequency of M1 and M2, the two plate alternating currents being in phase opposition.

If sources 22 and 23 are equal and the tubes are of like characteristics in the absence of modulating potentials the carrier wave is substantially suppressed in the circuit 25. However, if as pointed out in my United States application #95519 filed August 12, 1936, the sources 22 and 23 are made unequal then in the absence of modulating potentials one tube amplifies more than the other and a finite carrier frequency potential arises across the parallel resonant circuit 25 even in the absence of modulating potentials from M1 and M2. If then modulating potentials are set up on grid 1 by M1 but not by M2 the plate alternating current of tube I9 will not be modulated while that of 18 will be modulated. In the presence of modulating potentials at M1 and M2 an alternating potential of carrier frequency will appear in current resonance circuit 25, resulting from the difference of the plate alternating currents of the two individual tubes and this alternating potential will be modulated in-accordance with the modulating potentials of M1 as well as of M2.

The connection proposed in accordance with invention of the modulation potential sources to separate electrodes is Worthy of notice for the reason that the possibility is thereby insured to ground each modulation potential generator onesided so that all interferences are completely avoided that occur if several modulation potential sources must be connected in series to each other in the circuit of a control grid.

I claim:

1. In a signalling system, a pair of electron discharge tubes each having an anode and a plurality of auxiliary electrodes, means for applying wave energy in phase opposition to like auxiliary electrodes in said tubes, means for applying a plurality of sources of different modulating potentials each of said modulating potentials occupying a difierent frequency band to corresponding auxiliary electrodes in said tubes, and an output circuit connected to the anodes of said tubes.

2. In a modulation system, a pair of electron discharge tubes each having a cathode, an anode and a controlling electrode, means for applying wave energy to be modulated in phase opposition to said controlling electrodes, an alternating current circuit connecting the anode to cathode impedances of said tubes in parallel whereby the wave energies impressed on the controlling electrodes of said tubes oppose in said alternating current circuit, means for impressing separate operating potentials on corresponding electrodes of said tubes to control amplifying characteristics of said tubes so that the resultant wave.

energy appears in said alternating current circuit, and means for impressing plurality of sources of different modulating potentials each of said modulating potentials occupying a different frequency band on the controlling electrodes of said tubes.

3. In a modulation system, a pair of electron discharge tubes each having a cathode, an anode and a plurality of grid electrodes, means for applying wave energy to be modulated in phase opposition to like grid electrodes in said tubes, means tying the anodes of said tubes together, means tying the cathodes of said tubes together, an alternating current circuit connected between the anodes of said tubes and the cathodes of said tubes whereby the wave energy impressed on the grids of said tubes oppose in said alternating current circuit, means for impressing separate operating potentials on corresponding grid electrodes of said tubes to control amplifying characteristics of said tube so that resultant Wave energy appears in said alternating current circuit, a source of modulating potentials of a predetermined frequency band connected with a grid of one of said tubes, and a second source of modulating potentials occupying a frequency band different from said predetermined frequency band connected with a grid of the other of said tubes.

4. A system as recited in claim 2 wherein the modulating potential sources are each grounded at one terminal.

5. A system as recited in claim 3 wherein the modulating potential sources are each grounded at one terminal.

RUDOLF URTEL. 

